This is a revised submission of a request for continuation of a project aimed at studying functional recovery of penile and external anal sphincter ('sacral') spinal cord reflexes after contusion injuries in rats meant to model human spinal cord injury (SCI). Recovery of sacral reflexes was compared to recovery of locomotion. Serotonergic (5-HT) descending systems are thought to be involved in this recovery, and in the previous funding period, evidence was provided for denervation and reinnervation of sacral MNs by 5-HT after SCI. The source of the 5-HT sprouting is thought to be the small number of axons that remain in the spared rim of fibers after severe contusion SCI. We have shown that glial restricted precursor cells (GRPs) can be transplanted into contusion injuries, and that they alter the lesion environment by reducing glial scarring. The revised submission focuses on the hypothesis that the transplantation of GRPs into the contusion lesion cavity after SCI will result in more 5-HT sprouting and will enhance the recovery of sacral reflexes and locomotion. In aim 1, we will compare the long-term recovery of sacral and locomotor functions in rats receiving contusion lesions with and without GRP transplants given at 9-10 days following injury. In aim 2 we will compare the amount of serotonergic input to identified external anal sphincter (EAS) and bulbospongiosis (BS) motoneurons (MNs) in rats with and without GRP transplants. In aim 3, we will examine the source of the sprouting into the sacral cord by labeling brainstem sources of 5-HT with anterograde tracers combined with 5-HT IHC. This will also allow us to test the hypothesis that the reinnervation of the cord by spared descending systems maintains the specificity of the original connections. These studies represent a collaboration between laboratories studying SCI and developmental biology, and are intended to provide guidance on the possible therapeutic value of glial precursor transplantation in SCI.